Ahh, Coxy...

7A has the worst engine management [or, let's say, expensive] of all old audis and ke-jet is only next to it
As far as I remember, most latvian 7A users lost spark because of ignition timing sender fault - either some of senders is gone or pin on flywheel is gone. Also there is possibility that igniton distributor gear is gone - sometimes this happens to 7A and 3B.
P.S. All fuses in place?